Evaluation of coal tar fractions for use in psoriasiform diseases using the mouse tail test. (I) High and low temperature tars and their constituents.

'High' and 'low' temperature tars were evaluated on parakeratotic mouse tail skin, which was used as a model for the psoriatic keratinization process. The skin was examined histologically for signs of induced granular layers in previously scaly areas; epidermal thicknesses were also measured. It appears that the acidic (phenolic) fractions of coal tars induce granular layers and cause epidermal thickening, whereas neutral constituents alone only cause thickening. It is suggested that tar acids should be further investigated for anti-psoriatic activity.